a software program for Windows 3.1. The program let users design and print business cards on Avery and other brands of card stock that was pre-perforated for easy separation into individual cards. I knew the exact dimensions of the card stock, which were used in the software coding, to create the printed result. The design, of course, showed on the computer monitor, in perfect scale and with all the images and fonts and colors, etc. That was easy.
But, there was a problem with the printer business. Every printer company had to write printer drivers that worked with Windows 3.1, and later versions. They weren't always perfect, those drivers. The card stock, however, was very precisely laid out, within .001". There was no way, in Windows, to determine the quirks of those printer drivers, which meant that the designs might be off center on the cards by as much as .15 inches. That's quite visible in the printed card. Not acceptable.
Since I had no way to know what printers my potential customers might have, it was a problem that demanded a solution. Microsoft was no help at all, since they didn't create the printer drivers. So what's a software designer and coder to do?
Fudge factors. There was a menu item labeled "Fudge Factor" under "Format" on the software interface. In the program's manual and in a dialog box, I instructed users to first print an alignment page on plain paper and then hold that against the card stock with a light behind the two. Then, they measured the offset from perfection and provided horizontal and vertical fudge factor numbers in 1/100s of an inch plus or minus. Once that was done, the software stored those numbers in the program's configuration file and reloaded it every time the program ran. The user only had to find and enter that fudge factor once, as long as they used the same printer.
Was that solution a kludge? it certainly was. But nobody ever complained about that. One they had done the alignment process, the program printed precisely aligned cards every time.
Perhaps that's all that's missing in the cosmology calculations. A constant that is the "fudge factor" for this particular universe. 
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